COPPERAS
Etymology
Noun
copperas (usually uncountable, plural copperases)
iron(II) sulfate.
Source: Wiktionary
Cop"per*as, n. Etym: [OE. coperose, F. couperose, fr. (assumed) L.
cuprirosa, equiv. to G. cha`lkanqos, i. e. copper flower, vitriol.
See Copper and Rose.]
Definition: Green vitriol, or sulphate of iron; a green crystalline
substance, of an astringent taste, used in making ink, in dyeing
black, as a tonic in medicine, etc. It is made on a large scale by
the oxidation of iron pyrites. Called also ferrous sulphate.
Note: The term copperas was formerly synonymous with vitriol, and
included the green, blue, and white vitriols, or the sulphates of
iron, copper, and zinc.
Source: Webster’s Unabridged Dictionary 1913 Edition